Derek opens his mouth to reply to Stiles, but closes it the minute he hears Matches-- no, Batman-- come back, looking right at him as he does so. His nostrils flare a little bit, jaw set, and he reaches out to put a hand on Stiles' shoulder. His grip is firm, and Derek makes the intention clear: I don't trust you to take care of him.

(Derek barely trusts himself to take care of Stiles, but someone has to, someone has to make sure he's okay and alive and can get home to his family.)

"He'd be fine, anyway. He's with me."